| Resumo : |
This thesis aims to demonstrate a new method to produce thin black TiO2 films from pure TiO2 films in the anatase phase. The method consists of immersing the TiO2 films for fifteen minutes in a hydrogen plasma generated by a PECVD-RF system with a hollow cathode geometry, resulting in an efficient darkening of the TiO2. The growth of pure TiO2 films in the anatase phase on glass and c-Si substrates was carried out using a magnetron sputtering system and subsequent heat treatment at 450 °C for 2h in order to achieve a preponderance of the anatase phase. Before and after the H2 plasma treatment, the samples were characterized for their morphological, microstructural, chemical, optical, electrical, and wettability characteristics. For this purpose, analyzes of mechanical profilometry, scanning electron microscopy by field emission and atomic force, UV-Vis-NIR spectrophotometry, X-ray diffraction, Raman spectroscopy, X-ray excited photoelectron spectroscopy, measurements of sheet resistance by four-point probe, and goniometry. In addition, the photocatalytic potential of the films produced through the degradation of the methylene blue dye was evaluated, in addition to an investigation of the characteristics of the hydrogen plasma generated during the hydrogenation process. The results obtained show that the use of a hollow cathode for the hydrogenation process was decisive for the efficient hydrogenation of the black TiO2 films. After treatment in hydrogen plasma, the films show a significant increase in the absorption of light across the solar spectrum, a significant decrease in sheet resistance, and a significant increase in the surface area. These results are mainly related to an increase in O vacancies and an increase in the presence of OH hydroxyl groups on the surface of the films. These characteristics led to a significant improvement in its photocatalytic activity under UV-Vis irradiation.. |